I. Field of the Invention
This invention relates generally to remote automatic communication systems and more particularly to a reading and control system for reading the measurement of commodities and status switches at remote terminal points along a utility power transmission network, and controlling loads and alerts at the terminal points.
II. Description of the Prior Art
Utility Companies have long used meter reading personnel for reading the consumed commodity information provided by utility meters (i.e., gas, water, electricity and the like). However, in recent years significant strides have been made in the development of fully automatic meter reading systems.
Most remote meter reading systems have similarities in their designs. Generally, they comprise some type of encoder device attached to a meter to give an indication of the meter reading, means for storing the meter reading indicated and a transponder for transmitting meter data over a communication link to a central station when interrogated by a signal from the central station. Various types of communication links have been used in transferring the meter data from the individual meters to the central station. One system utilized a mobile van carrying a transmitter for interrogating meter equipment transponders. The interrogated transponders would then return messages to the van, which messages included meter identification and reading. Various other types of systems have been developed which utilize the telephone lines of the subscribers as the communication link to the central station. Also, there are arrangements in which the power lines of the subscriber and the utility company are used as the link between the customer's meter and the central station. One such arrangement is described in U.S. Pat. No. 4,135,181, issued on Jan. 16, 1979 to Bogacki, et al and which is assigned to the assignee of the present invention.
The Bogacki, et al arrangement comprises a central station which includes a computer with input-output equipment for the multiplex generation of commands and the multiplex receipt of data over a plurality of communication lines. A control unit is connected to a communication line and provides signal transmission and coupling of commands and data between the central station and a utility power line. The control unit includes means for recognizing addresses as well as means to decode a function code contained in commands received from the central station. When a control unit recognizes an allowable address in a command, it transfers that command to its connected power line. If the command function code specifies that the control unit is to receive a data message from the power line, the control unit will go into a receive mode after it has transferred the command.
The system also includes a meter terminal unit located at each customer residence. Each meter terminal unit is connected to the power line, and receives commands from and transmits messages to the control unit over the connecting power line. Each meter terminal unit is capable of selectively communicating with a plurality of utility meter encoders for reading a plurality of meters and for selectively driving a plurality of loads at a customer residence. Each meter terminal unit responds to specific commands to either selectively read and store data into one of several storage means from a plurality meters as specified by the command function code; selectively transmit the previously stored meter data from the several storage means to its associated control unit; or selectively control the operation of the residence's loads as specified by the function code.
Although the system of Bogacki, et al was a significant improvement over other prior art systems, it suffered from several disadvantages. These disadvantages include the relatively slow data through-put rate due to the slow bit rate, as well as the wait by the control unit for return messages after transmitting the message request commands. Another disadvantage is related to the number of meter terminal units which can communicate with a control unit. In a geographically widespread area, a meter terminal unit would have difficulty returning messages to the control unit unless a relatively high power, relatively expensive transmitter was included within that particular meter terminal unit. This would not only increase the expense of the system, it could also create the necessity to build more than one model meter terminal unit, depending on the remoteness of the meter terminal unit from its respective control unit.
A further disadvantge concerns the relative insecurity of the system regarding customer load control. This concern is manifested in that assurance must be provided that a load will be restored after being turned off by the system. In addition, assurance must also be provided that premium rate billing for customer consumption during certain predetermined peak periods is performed only during those periods and not at other times.
Consequently, it can be seen that a faster, more reliable system, having relatively few different models of components, which can be tailored in the field to accommodate future changes by the using utility company, is highly desirable.